Organic Light Emitting Diodes (OLED), as they have advantages of wide viewing angle, high contrast ratio and high response speed, etc, has drawn more and more attention. An OLED typically includes a first electrode, an organic light emitting layer and a second electrode. Currently, an organic light emitting layer of an OLED is generally formed by an etching process, in which an organic light emitting material is deposited on a substrate through evaporation for forming the organic light emitting layer. Such process needs a high resolution mask. To reduce production cost, a thin mask is a general choice. Further, to achieve a high resolution and high control accuracy, an opening with a mini-size may be needed to be formed in the mask. However, the conventional etching process has the following disadvantages: 1, because the mask is very thin, it is difficult to accurately control the size and location of the openings and to form the openings with a small size; 2, it is difficult and costly to manufacture a thin type mask, and the thin type mask has a relatively short lifetime.